KINETIC STUDY UNDER NON-ISOTHERMAL CONDITION FOR SILICON PURIFICATION
ESTUDO CINÉTICO EM CONDIÇÕES NÃO ISOTÉRMICAS PARA PURIFICAÇÃO DE SILÍCIO
Rodrigo Ramos Silva, Willian Boneli De Almeida, Rozineide Aparecida Antunes Boca Santa, Elídio Angioletto, Humberto Gracher Riella
Abstract
This study aims to evaluate the process of acid leaching, in HCl, for purification of silicon metal, obtained by magnesiothermic reduction of silica and promote greater removal of impurities. The reaction product formed is a powder which is physically and/or chemically bound, with approximately 75% of MgO and approximately 25% of silicon metal, among other elements. Acid leaching is an technique used in the solubilization of oxides by an acid solvent. The silicon metal with purities up to 94% can be obtained in one step. Thus, it has been tested the effect of the following concentration of hydrochloric acid HCl (1, 2, and 3 M), temperature (50, 65, and 80º C) and time (60, 90 and 120 min). The leaching kinetics was studied under non-isothermal condition. After the treatments, it was shown that concentration is the main effect of leaching. In some analyses, it was possible to convert up to 76%, i.e., 99.66% of MgO has been extracted.
Keywords
Resumo
Este trabalho teve como objetivo avaliar o processo de lixiviação ácida em HCl para remoção de impurezas e purificação de silício metálico obtido por redução magnesiotérmica de sílica. O produto de reacção formado é um pó que está fisicamente e/ou quimicamente ligado, com cerca de 75% de MgO e aproximadamente 25% de silício metálico, entre outros elementos. A lixiviação ácida é uma técnica utilizada na solubilização de óxidos por um solvente ácido. O silício metálico com purezas até 94% pode ser obtido em uma etapa. Assim, foi testado o efeito da seguinte concentração de ácido clorídrico HCl (1, 2 e 3 M), temperatura (50, 65 e 80º C) e tempo (60, 90 e 120 min). A cinética de lixiviação foi estudada sob condições não-isotérmicas. Após os tratamentos, foi demonstrado que a concentração é o principal efeito da lixiviação. Em algumas análises, foi possível converter até 76%, isto é, 99,66% de MgO foram extraídos.
Palavras-chave
References
1 Roskill. A report - Silicon and Ferrosilicon: Global Industry Markets & Outlook. [cited 2015 Mar 4]. Available at: https://roskill.com/market-report/silicon-ferrosilicon/.
2 Luque A, Hegedns S. Handbook of photovoltaic science and engeneering. 2nd ed. Hoboken: John Wiley & Sons Ltd.; 2011. 157-179.
3 Banerjee HD, Sen S. Investigations on the production of silicon from rice husks by the magnesium method. Materials Science and Engineering. 1982;52:173-179.
4 Vyazovkin S, Burnham AK. ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data. Thermochimica Acta. 2011;520(1-2):1-19.
5 Demirbas A. Non-isothermal leaching kinetics of braunite in water saturated with sulphur dioxide. Resources, Conservation and Recycling. 1999;26:35-42.
6 Fruhwirth O, Herzog GW, Hollerer I, Rachetti A. Dissolution and hydration kinetcs of MgO. Surface Technology. 1985;24:301-317.
7 Xia H, Peng J, Niu H, Huang M, Zhang Z, Zhang Z, et al. Non-isothermal microwave leaching kinetics and absorption characteristics of primary titanium-rich materials. Transactions of Nonferrous Metals Society of China. 2010;20:721-726.
8 Maitra S, Mukherjee S. Non-isothermal decomposition kinetics of magnesite. Cerâmica. 2007;53:284-287.
9 Raschman P, Fedotoročková A. Study of inhibiting effect of acid concentration on the dissolution rate of magnesium oxide during the leaching of dead-burned magnesite. Hydrometallurgy. 2004;71:403-412.
10 Raschman P, Fedorocková A. Dissolution of periclases in excess of hydrochloric acid: study of inhibiting effect of acid concentration on the dissolution rate. Chemical Engineering Journal. 2006;117:205-211.
11 Peng JH, Liu CP. Kinetics of sphalerite leached by FeCl3 in microwave filed. Zhongguo Youse Jinshu Xuebao. 1992;2:46-49.
12 Coats AW, Redfern JP. Kinetic Parameters from Thermogravimetric Data. Nature. 1964;1:201.
Facebook
Google+
Twitter
LinkedIn
Mendeley
StumbleUpon
CiteULike
Reddit
Email